Trial production of automatic sweep Fourier transform microwave spectrometer designed for 1GHz region

本课题的目的是试制一种用于低频区的灵敏分子束傅立叶转移微波光谱仪。该区域的光谱适用于包括两个或三个苯环在内的较大分子（作为许多生物分子的一部分）的高分辨率光谱。首先，我们改进了分光计，使分子束的方向与微波传播方向平行。这一改进是由Grabow （Kiel Uni）建议的。（德国）和Lovas （NIST，美国），我们对之前的水平更加敏感。第二步，我们用两个凹面镜构造了一个法布里-珀罗腔。一面镜子固定在气缸上，通过真空罐的法兰孔前后移动，用于调节频率。它很容易加热固体样品，如生物分子。经过几次试验，我们遇到了一些关于镜像排列和调优的严重问题。现在我们正在尝试设计和制造一种新的模型；(1)两个精确的rails设置真空罐和连接法兰的直角。(2)两个大反射镜（直径：550mm）分别固定在法兰上。我们可以用特殊的工具以低成本制作一个大镜子。购买了频率自动扫频机构的电子元件，并搭建了电路。从NIST组获得一个控制程序并转移到我们的系统。我们这个项目的最终目的是确定生物分子和水之间复合物的分子结构，具体的例子是苯甲酸和水，以及儿茶酚和水。我们曾尝试用旧的FTMW光谱仪测量这些配合物的光谱，但无法获得谱线。应发展固体样品的新技术，包括激光烧蚀。

The purpose of this project is a trial production of a sensitive molecular beam Fourier transfer microwave spectrometer designed for low frequency region. Spectrum in this region is suitable for high resolution spectroscopy of rather large molecule including two or three benzene rings( as a part of many biomolecules).At first, we improved our spectrometer to be change the direction of molecular beam to be parallel that of microwave propagation. This improvement was advised by Grabow (Kiel Uni., Germany) and Lovas (NIST, USA) and we got more sensitivity to previous level.Second step we constructed a Fabry-Perot cavity with two concave mirrors. One mirror fixed to cylinder which moved for and back through a flange hole of vacuum tank for tuning the frequency. It was easy to heat a solid sample like biomolecule. After several trials, we met some serious problems about mirror arrangement and tuning.Now we are trying to design and make a new model ; (1) two precise rails are set up out side of the vacuum tank and attached to both flanges on right angle. (2) two large mirrors (diameter : 550mm) fixed to Flange respectively. (3) we can make a large mirror by special tool on low expense.The electronic parts for frequency auto sweep mechanism were purchased and set up the circuit. A control program was obtained from NIST group and transferred to our system.Our final purpose of this project is to determine a molecular structure of the complex between biomolecule and water for concrete examples are benzoic acid and water, and catechol and water. We have already tried to measure spectrum of these complexes using old FTMW spectrometer, however could not obtain the spectral lines. New technique for a solid sample should be developed, including laser ablation.